Back in January this year I wrote a blog post about Skype for Business Interop with Teams and how to deploying Teams side-by-side with Skype for Business, how to configure the interop policy and getting teams users and skype users together on a meeting, Limitations of the interop at that time were also discussed. Last month Microsoft released new updates to the interop capabilities and this post serves as an update to what's changed and how to deploy Skype and Teams side by side moving forward.

Just to recap, in the January blog post we want to configured a tenant-wide policy to use Skype for Business as the default calling client while allowing users to override, by running the cmdlet as shown below:

However, as of the May update Microsoft no longer allows creating custom interop policies and the 'New-CsTeamsInteropPolicy' is no longer available in powershell. In addition, its no longer supported to allow end users to override the default calling client and setting different clients for chat and calls. This means that the administrator now must decide whether to use Skype or Teams for both calling and chat. So first we need to undo what we've done by running the Remove-CsTeamsInteropPolicy cmdlet as shown below:

This effectively makes both Teams and Skype for Business independent of each other a.k.a. an 'Islands' policy where Skype calls stay on Skype and Teams calls stay on Teams. However, Skype user can still IM a Teams user and vice versa but audio or video calls across the two different clients will go to voice mail. Moreover, Microsoft now only supports the following three built-in interop policies to be assigned to users:

All other interop instances are not supported and will be removed in future. In fact, the CsTeamsInteropPolicy will be removed in the future and replaced by CsTeamsUpgradePolicy which is already available in the tenant as shown below::

Obviously the default 'Islands' policy is not ideal for customers who primarily use Skype for business communication and Teams for collaboration as we would want users from both sides to be able to call each other over audio and video. So lets set a tenant wide policy to have Skype as the default calling/chat client by assigning the 'DisallowOverrideCallingSfbChatSfb' policy to our users by running the Grant-CSTeamsInteropPolicy. At the same time, to compliment this we also need to assign users the 'SfBWithTeamsCollab' policy for the CsTeamsUpgradePolicy. Example for our tenant is shown below:

We have to restart the Skype and Teams clients for the new policies to take effect. Now when a user on Teams calls a user who is logged into Skype, the call will get connected with Audio/Video capabilities. However, content sharing can be done only from the Skype user and will still require the Teams user to be logged into Skype which will be used to display content.

For more details on the interop configuration this article is a good place to start: ​https://docs.microsoft.com/en-sg/microsoftteams/migration-interop-guidance-for-teams-with-skype